Prop brainwave

[ghostlymoron]

I've just been thinking about 2 and 3 blade and folding props. I was wondering whether you could reduce prop resistance by glassing some deflectors on the hull just forward of the prop. These would taper so present little impedance to water flow. Or is this carp?

 

[Dipper]

I would have thought that they would impede water flow when you want drive from your prop. Or is this carp?

 

[trapezeartist]

I have a mental picture of what I think you are suggesting. A close fitting fairing in front of the prop would deflect water around the prop, though it would then be left to swirl and eddy back behind the prop. When sailing, the drag would probably be similar to a normal fixed prop. When motoring, the performance would be much worse than a folding prop. And it really wouldn't matter what sort of fish was swimming by at the time.

But well done for at least giving it some thought.

 

[ghostlymoron]

I was thinking of maybe 2 deflectors shaped like mickey mouse ears (only upside down) at the aft end and tapering to a point forrard. they would line up with the prop blades when stopped - possible the blades would self park or the shaft could be marked or have a stop. Probably talking carp but deffo 'blue sky thinking'.

 

[penfold]

It's carp; in order to function efficiently the prop must 'see' clean flow to it as the vessel moves, if you put fairings in front of it you disrupt this flow. Even P or A brackets and propshafts cause disturbance to the flow.

 

[awol]

I park my two-bladed prop vertically behind my skeg. I have convinced myself without any empirical data that this adds to my speed and is worth the risk of the gearbox sticking in reverse. The OP would probably be better putting up with the noise and letting the prop spin.

 

[prv]

I was thinking of maybe 2 deflectors shaped like mickey mouse ears (only upside down) at the aft end and tapering to a point forrard.

As TrapezeArtist implies, to minimise drag it's not enough just to have a pointy front. Your deflectors would need to also taper back to a point at the rear, and then they would no longer be doing their job as deflectors.

Lining a 2-blade prop up behind a skeg (or a long keel) helps a bit, given that the skeg was going to be there anyway. But adding a skeg purely to hide the prop behind it will not result in less drag.

Pete